MINING www.geolsoc.org.uk/factsheets Image left: Bingham Canyon open-pit copper mine, USA Image centre: Copper ore (azurite and malachite) Image right: Underground mine tunnel Image below: Drilling for rock core Mining is the underground extraction of minerals Exploring for mineral deposits from economically valuable deposits (such as metal-bearing ore-bodies, coal and gemstones). Mining and exploration companies The surface extraction of a wide range of minerals undertake investigations to look for is termed quarrying. Large surface operations are potentially economic mineral deposits. referred to as open-pit mines. Nowadays most undiscovered deposits do not outcrop at the surface so Mining is carried out on the surface and underground: geologists use techniques that provide information about rocks underground to Open-Pit mining is used for less complex, usually larger, mineral estimate the quantity and concentration deposits which occur near the Earth’s surface (typically less than of a metal or mineral present in a 1km deep). This involves excavation of the mineral and the deposit. overlying material (known as ‘overburden’). It is generally cheaper than underground mining. Exploration techniques include: Using Geophysics to look for variations in gravity or the Underground mining is used for more complex, sometimes smaller, Earth’s magnetic field. deeper mineral deposits. These methods produce much less waste Testing soil chemistry. rock, but are usually much more expensive than open-pit mining. Drilling and analysing rock core. How much metal do we mine every year? Iron Copper Nickel Silver Gold Platinum DID YOU KNOW? 2.9 billion 18 million 1.9 million 25,000 3,000 180 The deepest open-pit mine in the world is tonnes tonnes tonnes tonnes tonnes tonnes Bingham Canyon Copper Mine, Utah, USA. It is Increasing value and scarcity nearly a kilometre deep! The weight of ore mined before the metal can be extracted is even The deepest underground mine is the Mponeng higher than the figures above, and the concentration of metal in ore Gold Mine, South Africa. Its deepest level is almost (the ‘grade’) also varies. Although we extract about one million times 4 kilometres below the surface. At this depth, the more iron than gold, the grade of gold ore is so much lower than that rock is so ho the mine uses of iron that similar volumes of rock are extracted for both metals. 6,000 tonnes of ice a day for refrigeration. MINING www.geolsoc.org.uk/factsheets How do we extract and process minerals? Mining in the UK 1. MINING STAGE Mining and processing minerals (separating useful products from waste) needs some really big toys! The UK’s mining heritage Mining techniques stretches back to the Bronze Drills are used to analyse rocks and load explosives. Age. Devon and Cornwall were Explosives are the most common way to excavate rock. once among the most Excavators move the excavated rock to trucks. Large excavators used in productive areas for tin and open-pit mines can hold 70 tonnes of rock. Underground mines use smaller copper in the world, and versions known as ‘scoops’ or ‘dumpers’. Enormous ‘bucket-wheel Scotland, Wales and Northern excavators’ are used in some open-pit coal mines. Ireland all have histories of Trucks take rock from the excavator to the processing plant, and can be metal mining. Coal mining was huge - the largest can carry 450 tonnes, or the mass of a fully loaded formerly a huge industry across Boeing 747. Some mines use driverless trucks controlled by computer. central and northern England and Wales. Processing techniques The industry declined during Crushers & mills break up the rock and expose minerals for processing. the later 20th Century, and in Froth Flotation separates ore minerals, which float, and waste, which sinks. 1998 the closure of the South This forms a metal ‘concentrate’ which can be ‘smelted’ (heated with Crofty Tin and Copper Mine in various compounds) to produce metal. Cornwall left the UK without an Explosives image © Vicky@Canada / Flickr active metals mine for the first Critical Metals time in centuries. The last Many metals like iron and aluminium are relatively abundant. However, nowadays we use a huge variety underground coal mine in the of rarer elements; for example, about 60 different elements go into a smartphone. Most are used in UK, the Kellingley Colliery, also small quantities and many are deemed ‘critical’ (at risk of supply shortages) by the European Union. closed in 2015. Critical element Produced in Reasons for criticality Some uses However, in 2008 the • Single producing nation Magnets in Cavanacaw Gold Mine opened Rare Earth China • No substitutes electronics, laser near Omagh in Northern Elements (90%) • Difficult processing technology Ireland, and in 2015, the Drakelands Tungsten and Tin • Only produced as a mine entered production near Chile, Turbofan jet Rhenium by-product of Plymouth in Devon. USA engines molybdenum mining The UK also continues to quarry Battery industrial and construction Australia, • Rarity Lithium technology for minerals such as sand and clay. Chile • Few producing nations electronics Images: Rhenium © Alchemist-hp / Wikimedia, Lithium © Tomihahndorf / Wikimedia Responsible mining and environmental issues As well as ensuring the safety of the people who work there, mines have important environmental responsibilities. Processing can involve toxic substances (such as cyanide, used to extract gold) so careful management is essential. This continues for many years after mine closure, as weathering of waste ores can release acidic water containing arsenic or lead. Abandoned tunnel collapses can also cause subsidence on the surface, and tips of waste rock have to be carefully constructed and maintained. Innovative techniques are used to address these issues, and many former mines are important ecological sites with rare plant communities, as well as being great places to study geology! Drakelands Mine, Hemerdon, Devon .